Conventionally, when a ladder program of a programmable logic controller (PLC) is created with a program creation device, a program creator selects an icon displayed on a list on a tool bar, a pallet or the like, using a pointing device such as a mouse, in order to make insertion into a ladder diagram on an editor screen, or manually inputs a mnemonic with a keyboard.
In a method of selecting a programming item using a pointing device, when performing an operation to select a desired icon from a displayed list of icons of a plurality of programming items, a programming item that is different from a desired programming item may be selected sometimes due to his/her erroneous operation of the pointing device.
Furthermore, in a method of manually inputting a mnemonic with a keyboard, an input operation is complicated, which requires more effort of a program creator.
Patent Literature 1 discloses a technique for a device having a touch panel function, in which a plurality of icons are displayed in a ring-shaped arrangement, and according to a drag operation performed on a display unit, the icons arranged in a ring shape are rotated and moved in the drag direction.